The news about marijuana keeps getting worse.

As drug advocates pushed marijuana legalization over the last 15 years, they portrayed the drug as harmless, a mild intoxicant with few side effects. Cannabis – the term scientists prefer for marijuana – might even have medicinal value, advocates said.

The truth is the opposite.

Even in states, from Maine to California, that have legalized cannabis, researchers have published paper after paper showing its risks, particularly to heavy or daily users. I do not mean the munchies or falling asleep on the couch. Powerful evidence links the drug to heart attacks, strokes, severe mental illness, and even suicides.

Cannabis and its active ingredient, the chemical called THC, are toxic to the heart and brain. They are also much more addictive than many users realize. Though cannabis does not cause the physical dependence of alcohol, it can make users psychologically dependent, leading to irritability, depression, and mood swings if they cut back. And a huge new study shows that legalization is linked to a sharp increase in diagnoses of cannabis addiction.

As more Americans see the problems firsthand, their views of cannabis are slowly turning negative, a recent Gallup poll found. Even in deep-blue New York, almost twice as many residents say cannabis legalization has hurt their quality of life as helped it.

But just as it took decades for the public to realize the cancer risks of cigarettes, the health harms of cannabis are not completely understood. A majority of Americans still favor legalization – a fact that makes the emerging science even more alarming.

In March, scientists in Boston reported cannabis users under 50 had a sixfold higher risk of heart attacks compared to people who didn’t. In February, Canadian researchers found people hospitalized with a diagnosis of cannabis abuse were six times as likely to die as the average person over the next five years. Suicides and trauma-related deaths made up much of the increase.

The research on the psychiatric harms of cannabis is also piling up.

The connection between cannabis and severe mental illness, including the psychotic disorder schizophrenia, comes as no surprise to me. In 2019, I wrote the book "Tell Your Children: The Truth About Marijuana, Mental Illness, and Violence." At the time, drug legalizers and their media handmaidens sharply criticized the book. The Guardian, a leftist British newspaper, called it "pure alarmism."

Six years later, "Tell Your Children" has been vindicated. In April, researchers in Quebec found a crucial mechanism in the brain by which cannabis can cause hallucinations and delusions.. And just weeks ago, physicians in Colorado – the first state to legalize cannabis – reported that diagnoses of psychosis in young people have soared in the last 15 years, with diagnoses in heavy cannabis users driving the increase.

The science is clear.

Even for adults, cannabis isn’t safe, especially for daily use. For teens, whose brains are still developing, it is highly risky – and at worst can lead to lifelong psychiatric problems. It is addictive.

It is far more potent than a generation ago, and THC, its active ingredient, is now available in brightly colored gummies and other "edibles" that are the leading cause of poisonings in young children.

As The New York Times itself admitted last year:

As marijuana legalization spreads across the country, people are consuming more of the drug, more often and at ever-higher potencies… a growing number, mainly heavy users, have experienced addiction, psychosis and other harmful effects…

Meanwhile, the promises of cannabis legalization have not come true. Tax revenue from legal cannabis is a rounding error in state budgets, and legalization has not ended the illegal market in cannabis, which remains large and violent. If anything, legal stores are actually losing ground to illegal dealers at this point.

The core reason is that legal sellers face regulations, taxes, and insurance costs that illegal sellers do not. Illegal sellers can undercut the legal price. And the heavy users who buy most cannabis want the lowest price, legal or not.

Thirteen years after Colorado became the first state to legalize recreational cannabis, the experiment has failed. But powerful economic forces and the media’s refusal to admit what’s really going on mean that most Americans don’t know the truth yet.

Eventually, they will.

In the meantime, Tell Your Children – cannabis is far from benign.